Efforts have been made to contain various types of contaminants at oil and gas well sites. For example, at non-conventional shale gas drilling sites, there are large quantities of fuel, drilling mud, fracturing chemicals, corrosives and flowback water. Spills of any of these liquids must be reported to regulatory agencies, and the contaminated soil and water must be remediated. To reduce the amount of contaminated soil and water and to eliminate regulatory fines, many operating companies excavate the site, cover it with stone or crushed rock, place a geotextile over the crushed rock, and then loosely place a geomembrane over the surface. For non-conventional shale gas drilling sites, the preferred geotextile is an 8 to 10 oz/yd2 needlepunched polypropylene felt and the geomembrane is a 20 to 60 mil thick high density polyethylene (HDPE). The geotextile protects the geomembrane from sharp edges in the stone or crushed rock base. The felt is either sewn or heat tacked together with a hot air tool. The geomembrane is then placed over the geotextile and welded together with a hot wedge welder, a hot air tool or an extrusion fillet welder.
Once the layers are installed at the well site, the geomembrane is pulled over earthen berms, railroad ties or corrugated pipe to form containment walls around the perimeter. The geomembrane then contains the leaks and spills for subsequent removal, e.g., until an on-site vacuum truck can remove them without impact to the environment.
There are issues with the current configurations. Traditional HDPE geomembranes for ponds and pits were not designed for foot and vehicle traffic. HPDE geomembranes are prone to punctures, e.g., from dropped hoses, vehicles and equipment movement. The geomembranes are also extremely slippery to work on, even with a textured surface. Friction treatment of geomembrane or geotextile surfaces to prevent slippage is disclosed in U.S. Pat. Nos. 5,056,960 and 5,137,393, respectively.
To increase traction in standing water, snow and ice, some operating companies now place, but do not bond, an additional layer of a geotextile over the HDPE geomembrane to reduce slip hazards. For example, an 8 to 10 oz/yd2 needlepunched polypropylene felt may be used for this purpose. While the geotextile improves traction on the top walking surface, it has disadvantages. The geotextile slides around on the geomembrane, producing a slip hazard. Geotextiles can bunch and can be pulled into vacuum hoses while removing liquids from the surface. Geotextiles can also absorb a considerable amount of fluid that then can freeze, negating any increased traction. Loose geotextiles can mask punctures in the geomembrane beneath it, which may only be discovered after a spill or leak. Furthermore, the geotextiles complicate the installation of grounding rods through the geomembrane, since the geotextiles need to be cut away so the geomembrane can be sealed to the grounding rod.
A polymer sheet that has geotextiles laminated on both sides is disclosed in U.S. Pat. No. 5,747,134 for use in ponds, landfills and hazardous and non-hazardous waste disposal. The covers and barriers are designed to provide primary containment, but not to withstand foot and/or vehicle traffic. Because this laminate is not subject to abrasion and/or shear forces, the three separate continuous layers can be joined together by tie layers or with adhesive. While this laminate protects the geomembrane from punctures on both sides, tie layers and adhesives are not adequate to prevent delamination under heavy vehicle traffic, such as cranes, frac tanks and track hoes at gas drilling pads. Once delaminated, the layers can move around and result in the same issues as the loose laid geotextiles. The continuous polymer sheet also leads to thick, stepped seams, which can be a tripping hazard.
The present invention has been developed in view of the foregoing.